Glass



Patented Apr. 26,1927,

ram) 1:. memoir vxc'ron. NE-W ironx.

class No Drawing. Application filed August 38, 1 9, Serial ll'o.117,827. Renewed October 89, 1928.

V The present invention relates 'to glasses and to batches for producingthe same, an

object of this inventlon'being to provide lowexpansionboro-silicateglasses which have high stability and.- arefree-frombrittlenes's. Prior to this invention, boro-silicate glasses oflow expansion have been known, but in an. such glasses. it has beencustomary to use alkali carbonates as a flux. I have discovered that bythe-elimination .of the'alkali carbonates and the use of alkalinitrates, as-potassium nitrate or sodium nitrate, in connection withboro-silicate glasses, that I I am able to obtain a'glass of lowerexpanslon with less-brittleness, and, in. connection with some batches,a pure white transparent glass may be obtained, where the same would beimpossible with batches employing alkali carbonates.

The following is an example of a batch made in accordance with thisinvention:

'80 parts silica or 10 parts boric acid, 10 parts'alkali nitrates, asfor instance 5 parts potassium nitrate; and 5 parts'sodiumnitrate.lOparts cryolite. And-1 art lepidolite. The le idolite facilitates t eworkin of the glass the features of this invention. The fluorine in the'cryolite permits the silica to be'fused ata lower temperature and inthis way per- ,mits the use of a greater amount of silica.

Another glass made in accordance with this invention has an" analysissubstantially as accordance with this invention gives an analysisapproximately, silica/(5%, B 0 15%, Li O 1%, A1 0,, 5%, Na O 4%. Thisglass has a .co-efiicient of expansion of approximately .0000040.

- Still another glass within this invention such at is not essential forsome 0 K What I claim as my invention Al O and lTeO shows an analysisapproximately as follows:

sio, B20, 13 Li,0 9 mp, 2

Sb,(), 6%. .This glass has a coefiicien't'o expansion ofapprox1mate1y,.000O056.

' g u N trite sin-T E si PA ENT mcee- Glasses made in accordance withthis invcn'- tion are extremely useful in the manufacture of articlesexposed to extreme variations of temperature and subject to attack by achemlcal action. 1 cooking vessels and culinary ware, they are Inaddition to their use :for'

also high] eflicient'insulators and particularly insu ators for carryinghigh Volta e current. It is apparent however, that the glass may be usedin the manufacture of any articlejwhich reeuires high stability andaexpansion. The nitrates low coeflicient 0 answer the purpose of afluxand at the same time give lower ex ansion and lessen thebrittleness. In addition they tend to also ,increase the stability. I amaware that it is old prior to this invention to use nitrates for the purose ofpurifying glass to makeit whiter, at in the compositionsheretoforev used, the nitrates have not had also the funcban of loweringthe expansion and reducin the. brittleness. I do not wish to be limite Ito secure byLetters Patent is:

' 1. A boro-silicate glass batch containing to the specific batchesherein specified, nor do: 1

and desire- 1 an alkali metal nitrate and a relatively large percenta ofsilica.

2. A g ass of high stability having a 00- I alumina.

4. A hero-silicate glass of high stability containing approximately 79%of silica, approximately 14% boric oxide asmall amount of alumina, andapproximate 5. A bore-silicate glass of high stability containingbetween 70 and 7 9 er cent of' silica, not above 28 per cent of ricoxide,

y 5% of alkali.

I Eer cent of alkali and formed by fusing a lowing analysis: SiO78.73%,a1ka ies 6.20%, a v

'not nbove 5 percent of aliimina, not above 9 7. A glass havingsubstantiall' the fol; tch containing a nitrate of an alkali. A1 0 andFeO .86%, 13 0 14.22%. 10

6. A glass having substantiallv the fol- In witness whereof I havehereunto set my T a lowing'anal sis: SiO' 78.73%, Li,0 1.337 hand this19;:11 day .of August, 1916; I

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